When a wireline 911 call is initiated, the call is directed to an assigned local Public Safety Answering Point (PSAP). The PSAP answers the call and receives an inbound telephone number or Automatic Number Identification (ANI) information. This number is used to query an Automatic Location Identification (ALI) database, match it with the corresponding address as a location of the caller, and forward the location information and inbound telephone number to the assigned PSAP. The PSAP can then deliver both the number and the location to the appropriate emergency service (e.g., fire, police and/or ambulance) for dispatch.
The above scenario works well when the 911 call originates from a residence because every residential number is associated with a unique, static residential address. For mobile devices, such as mobile phones, however, the location changes as the mobile device user travels to different locations. Accordingly, the FCC has advanced a technology known as enhanced 911 (E911) to enable mobile devices to process 911 emergency calls and enable emergency services to determine the location of a caller.
Prior to 1996, wireless 911 callers would have to access their service providers to get verification of subscription service before the call could be routed to a PSAP. In 1996, the FCC ruled that a 911 call must be routed directly to the PSAP without receiving verification of service from a specific mobile carrier. The FCC further ruled that the call must be handled by any available carrier even if the carrier is not the caller's home carrier. Under the FCC's rules, all mobile phones manufactured for sale in the United States after Feb. 13, 2000, must be able to operate in analog mode and must include this special method for processing 911 calls.
The FCC has proposed a phased rollout of E911. In 1998, Phase 1 was implemented and required that mobile carriers identify the originating phone number and the location of the base station or cell within a 1 mile accuracy. Phase I E911 rules require a 7, 8 or 10 digit number to accompany each 911 call. The number provides a callback number for the PSAP dispatcher to use if, for example, the call is disconnected.
In 2001, Phase II was implemented and required that each mobile carrier in the United States offer handset- or network-based location detection capability so that the caller's location is determined by the geographic location of the mobile phone within 100 meter accuracy. The FCC refers to this as Automatic Location Identification (ALI). Phase II E911 rules provide a more accurate location for the dispatcher to use.
The inventors postulate that the emergence of intelligent network services, such as call screening and call forwarding that enable wireless customers to screen incoming calls and forward incoming call to an alternate number, could create obstacles for 911 callbacks. For example, when a 911 call is disconnected, the PSAP will attempt a callback and the incoming call to the customer's mobile device will not include a tag or any special identifier to identify the call as originating from a 911 PSAP. The incoming call appears as normal incoming call to the mobile device. In some instances a calling party number is unavailable, resulting in an unknown number notification being displayed on the mobile device. With this lack of vital information, the call screening service cannot identify the incoming call as an emergency (911) callback. Moreover, if the customer has established call restrictions for their account, the emergency callback may be restricted entirely resulting in the customer receiving no identification as to an incoming call.
Call forwarding services could present another problem. When the PSAP performs a callback and the callback number is subject to a call forwarding request, the incoming callback is automatically forwarded to the forward destination number. A customer may select that only certain, perhaps important, numbers be forwarded while all others be terminated at the primary phone number. In addition, some customers may elect to forward all calls using a call forward unconditional (CFU) service.